System and method for non-invasively determining an indication and/or an assessment of intracranial pressure

ABSTRACT

A system for non-invasively determining an indication and/or an assessment of intracranial pressure (ICP) is featured. The system includes at least one intracranial light source adapted to be placed on skin above a cranium of a living subject configured to emit light which penetrates the cranium and targets intracranial space of a living subject. The system includes at least one extracranial light source adapted to be placed on skin above a predetermined area of the living subject configured to emit light which penetrates and targets extracranial space of the living subject. A detector subsystem including at least a first detector is configured to detect reflected light from the intracranial space and the extracranial space and is configured to output intracranial output signals associated with light detected from the intracranial space and/or output extracranial output signals associated with light detected from the extracranial space. A processing subsystem is coupled to the at least one intracranial light source, the at least one extracranial light source, and the detector subsystem. The processing subsystem is configured to determine intracranial oxygen saturation and extracranial oxygen saturation and non-invasively determine an indication and/or an assessment of ICP using a ratio of the intracranial oxygen saturation to the extracranial oxygen saturation.

RELATED APPLICATIONS

This application claims benefit of and priority to U.S. ProvisionalApplication Ser. No. 62/956,725 filed Jan. 3, 2020, under 35 U.S.C. §§119, 120, 363, 365, and 37 C.F.R. § 1.55 and § 1.78, which isincorporated herein by this reference.

GOVERNMENT RIGHTS

This invention was made with U.S. Government support under Contract No,W81XWH-17-C-0006, awarded by the U.S. Army. The Government has certainrights in the invention.

FIELD OF THE INVENTION

This invention relates to a system and method for non-invasivelydetermining an indication and/or an assessment of intracranial pressure(ICP).

BACKGROUND OF THE INVENTION

Traumatic Brain Injury (TBI) is a complex and heterogeneous disorderthat may result in a large spectrum of associated injury severity. Thebrain is a soft organ with delicate structures held within a fixedvolume. Damage to the small structures within a brain may cause localswelling (ICP) and cerebral blood flow and systemic blood pressure maynot necessarily decrease with brain swelling. This elevated ICP maycause more damage which may lead to a negative spiral that may result indire health sequelae which may include brain cell death and permanentbrain injury or death. In many active populations a person with a braininjury may try to ignore the seemingly mild symptoms of headache,dizziness and the like. However, an unknown percentage of such injuredpersons may be experiencing clinically significant elevated ICP whichmay worsen or lead to permanent brain damage. Early detection ofelevated ICP could reduce the risks associated with undiagnosed ICP andprovide for timely medical care including, inter alia, pharmacologicalor surgical interventions.

One conventional system and method to non-invasively monitor ICP relieson optical coupling with source probes and detectors and diffusecorrelation spectroscopy. See e.g., WO 2016/164891, incorporated byreference herein. Another conventional system for non-invasiveassessment of hemodynamic functional state of the brain teaches usingnear-infrared spectroscopy (NIRs) to transmit light through a body partwhich is measured by a light sensor. See e.g., U.S. Publ. No.2010/0268096, incorporated by reference herein. The '096 patentapplication teaches an optical measurement block which carriesinformation about the blood flow through the brain and the value ofintracranial pressure. Another known system for an oxygen saturationmeasuring sensor and oxygen saturation measuring apparatus teaches aplurality of light sources and a plurality of light receiving elementsthat detect the near-infrared, light having wavelengths corresponding tooxyhemoglobin and deoxyhemoglobin to calculate oxygen saturation. Seee.g., U.S. Publ. No. 2018/0110449, incorporated by reference herein.Non-invasively determining intracranial oxygen saturation andextracranial oxygen saturation is also known. See e.g., Yanagisawa etal., Partial Optical Path Length in the Scalp in Subject-Specific HeadModels For Multi-Distance Probe Configuration of Near InfraredSpectroscopy, Proceedings Volume 10711, Biomedical Imaging and SensingConference, (2018), incorporated by reference herein.

However, to date there appears to be no known robust and reliable systemor method that can non-invasively determine an indication and/or anassessment of ICP using measured intracranial oxygen saturation andextracranial oxygen saturation such that the proper medical care can beprovided to those who may have experienced trauma to the brain.

SUMMARY OF THE INVENTION

In one aspect, a system for non-invasively determining an indicationand/or an assessment of intracranial pressure (ICP) is featured. Thesystem includes at least one intracranial light source adapted to beplaced on skin above a cranium of a living subject configured to emitlight which penetrates the cranium and targets intracranial space of aliving subject. At least one extracranial light source is adapted to beplaced on skin above a predetermined area of the living subjectconfigured to emit light which penetrates and targets extracranial spaceof the living subject. A detector subsystem includes at least a firstdetector configured to detect reflected light from the intracranialspace and the light reflected from extracranial space and is configuredto output intracranial output signals associated with light detectedfrom the intracranial space and output extracranial output signalsassociated with the light detected from the extracranial space. Aprocessing subsystem is coupled to the at least one intracranial lightsource, the at least one extracranial light source, and the detectorsubsystem. The processing subsystem is configured to determineintracranial oxygen saturation and extracranial oxygen saturation andnon-invasively determine an indication and/or an assessment of ICP usinga ratio of the intracranial oxygen saturation to the extracranial oxygensaturation.

In one embodiment, the at least one intracranial light source mayinclude at least two light sources. One of the two lights sources may beconfigured to emit light at one or more first predetermined wavelengthsand the other of the at least two light sources may be configured toemit light at one or more second predetermined wavelengths. One of thefirst predetermined wavelengths or the second predetermined wavelengthsmay be configured to target oxyhemoglobin chromophores and the other ofthe first predetermined wavelengths or second predetermined wavelengthsmay be configured to target deoxyhemoglobin chromophores. The at leastone extracranial light source may include at least two light sources.One of the two light sources may be configured to emit light at one ormore first predetermined wavelengths and the other of the at least twolight sources may be configured to emit light at one or more secondpredetermined wavelengths. The at least one intracranial light source,the at least one extracranial light source, and the at least onedetector subsystem may be adapted to be placed on the skin above thecranium of the living subject with the at least one extracranial lightsource located between the at least one intracranial light source andthe at least one first detector. The at least one first detector may bespaced from the at least one intracranial light source by anintracranial separation distance that causes the at least one firstdetector to detect the light reflected from the intracranial space andoutput the intracranial output signals. The first detector may be spacedfrom the at least one extracranial light source by an extracranialseparation distance that causes the at least first detector to detectlight reflected from the extracranial space and output the extracranialoutput signals. The processing subsystem may be configured toalternately enable the at least one intracranial light source and the atleast one extracranial light source and alternately enable the firstdetector to detect the light which reflects from the intracranial spaceand the light which reflects from the extracranial space to generate theintracranial output signals and the extracranial output signals. Theprocessing subsystem may be responsive to the intracranial outputsignals and the extracranial output signals and further configured toreduce contributions from the extracranial space which may exist in theintracranial output signals and generate corrected intracranial outputsignals to increase accuracy of the indication of ICP. The detectorsubsystem may include a second detector adapted to be placed on one ofthe predetermined areas of the living subject. The second detector maybe placed proximate the at least one extracranial light source andspaced from the at least one extracranial light source by apredetermined extracranial separation distance that causes the seconddetector to detect light which is reflected from the extracranial spaceand output the extracranial output signals. The processing subsystem maybe coupled to the at least one intracranial light source, the at leastone extracranial light source, the first detector, and the seconddetector. The processing subsystem may be configured to alternatelyenable the at least one intracranial light source and the at least oneextracranial light source and alternately enable the first detector todetect the light reflected from the intracranial space and alternatelyenable the second detector to detect the light reflected from theextracranial space and generate the intracranial output signals and theextracranial output signals and may be further configured to reducecontributions from the extracranial space that may exist in theintracranial output signals and generate corrected intracranial outputsignals to increase the accuracy of the indication and assessment ofICP. The intracranial oxygen saturation and/or the extracranial oxygensaturation may include one or more of: oxygen tissue saturation (StO₂),arterial oxygen saturation (SaO₂), or venous oxygen saturation (SvO₂).The system may further include a display device coupled to theprocessing subsystem configured to display one or more of the indicationand/or assessment of ICP, and/or the intracranial oxygen saturation,and/or the extracranial oxygen saturation, and/or a ratio of theintracranial oxygen saturation and the extracranial oxygen saturation,and/or a difference of the intracranial oxygen saturation and theextracranial oxygen saturation.

In another aspect, a system for non-invasively determining an indicationand/or an assessment of intracranial pressure is featured. The systemincludes at least one intracranial light source adapted to be placed onskin above a cranium of a living subject configured to emit light whichpenetrates a cranium of a living subject and targets intracranial spaceof the living subject. At least one intracranial detector is placedproximate the at least one intracranial light source and spaced from theintracranial light source by a predetermined intracranial separationdistance that causes the intracranial detector to detect the light whichreflects from the intracranial space and output intracranial outputsignals. At least one extracranial light source is adapted to be placedon the skin above a predetermined area of the living subject configuredto emit light which penetrates and targets extracranial space of theliving subject. At least one extracranial detector is placed proximatethe at least one extracranial light source and spaced from the at leastone extracranial light source by a predetermined extracranial separationdistance that causes the at least one extracranial detector to detectthe light which reflects from the extracranial space and outputextracranial output signals. A processing subsystem is coupled to the atleast one intracranial light source, the at least one intracranial lightdetector, the at least one extracranial light source senor, and the atleast one extracranial detector. The processing subsystem configured todetermine intracranial oxygen saturation and extracranial oxygensaturation and non-invasively determine an indication and/or anassessment of ICP using a ratio of the intracranial oxygen saturation tothe extracranial oxygen saturation.

In one embodiment, the processing subsystem may be configured toalternately enable the at least one intracranial light source and the atleast one extracranial light source and alternately enable the at leastone intracranial detector to detect the light reflected from theintracranial space and alternately enable the at least one extracranialdetector to detect light which reflects light which reflects from theextracranial space to generate the intracranial output signals and theextracranial output signals. The processing subsystem may be responsiveto the intracranial output signals and the extracranial output signalsand may be further configured to reduce contributions from theextracranial space which may exist in the intracranial output signals.The processing subsystem may be responsive to the corrected intracranialoutput signals and the extracranial output signals and may be furtherconfigured to determine the intracranial oxygen saturation and theextracranial oxygen saturation and non-invasively determine anindication and/or an assessment of ICP using a ratio of the intracranialoxygen saturation to the extracranial oxygen saturation to increase theaccuracy of the indication and/or assessment of ICP. The at least oneintracranial light source may include at least two light sources. One ofthe at least two lights sources may be configured to emit light at oneor more first predetermined wavelengths and the other of the at leasttwo light sources may be configured to emit light at one or more secondpredetermined wavelengths. One of the first predetermined wavelengths orthe second predetermined wavelengths may be configured to targetoxyhemoglobin chromophores and the other of the first predeterminedwavelengths or second predetermined wavelengths may be configured totarget deoxyhemoglobin chromophores. The at least one extracranial lightsource may include at least two light sources. One of the at least twolight sources may be configured to emit light at one or more firstpredetermined wavelengths and the other of the at least two lightsources configured to emit light at one or more second predeterminedwavelengths. One of the first predetermined wavelengths or the secondpredetermined wavelengths may be configured to target oxyhemoglobinchromophores and the other of the first predetermined wavelengths orsecond predetermined wavelengths may be configured to targetdeoxyhemoglobin chromophores. The at least one intracranial detector maybe spaced from the at least one intracranial light source by anintracranial separation distance that causes at least one intracranialdetector to detect the light reflected from the intracranial space andoutput the intracranial output signals. The at least one extracranialdetector may be spaced from the at least one extracranial light sourceby an extracranial separation distance that causes the at least oneextracranial detector to detect light reflected from the extracranialspace and output the extracranial output signals. The intracranialoxygen saturation and/or the extracranial oxygen saturation may includeone or more of oxygen tissue saturation (StO₂), arterial oxygensaturation (SaO₂), or venous oxygen saturation (SvO₂). The system mayinclude a display device coupled to the processing subsystem configuredto display one or more of: the indication and/or assessment of ICP,and/or the intracranial oxygen saturation, and/or the extracranialoxygen saturation, and/or the ratio of the intracranial oxygensaturation and the extracranial oxygen saturation, and/or a differenceof the intracranial oxygen saturation and the extracranial oxygensaturation.

In yet another aspect, a method for non-invasively determining anindication and/or an assessment of intracranial pressure by measuringoxygen saturation is featured. The method includes emitting light whichpenetrates a cranium of a living subject and targets intracranial spaceof the living space, emitting light which penetrates and targetsextracranial space of a predetermined area of the living subject,detecting light reflected from the intracranial space outputtingintracranial output signals, and detecting light reflected from theextracranial space and outputting extracranial output signals. Themethod also includes responding to the intracranial output signals andthe extracranial output signals and determining intracranial oxygensaturation and extracranial oxygen saturation and non-invasively anddetermining an indication and/or an assessment of ICP using a ratio ofthe intracranial oxygen saturation to the extracranial oxygensaturation.

In one embodiment, emitting light which penetrates the cranium of theliving subject and targets the intracranial space may include emittinglight at one or more first predetermined wavelengths and emitting lightat one or more second predetermined wavelengths. One or more of thefirst predetermined wavelengths may be configured to targetoxyhemoglobin chromophores and the other of the one or more firstpredetermined wavelengths or second predetermined wavelengths may beconfigured to target deoxyhemoglobin chromophores. Emitting light whichpenetrates and targets the extracranial space of the living subject mayinclude emitting light at one or more first predetermined wavelengthsand emitting light at one or more second predetermined wavelengths. Oneof the one or more first predetermined wavelengths may be configured totarget oxyhemoglobin chromophores and the other of the one or more firstpredetermined wavelengths or one or more second predeterminedwavelengths may be configured to target deoxyhemoglobin chromophores.The method may include alternately emitting light which penetrates thecranium of the living subject and targets the intracranial space of theliving subject and emitting light which penetrates and targets theextracranial space of the predetermined area of the living subject andalternately detecting light reflected from the intracranial space andoutputting the extracranial signals and alternately detecting lightreflected from the extracranial space and outputting the extracranialsignals and reducing contributions from the extracranial space that mayexist in the intracranial output signals in generating correctedintracranial output signals to increase the accuracy of the indicationand/or assessment of ICP.

The subject invention, however, in other embodiments, need not achieveall these objectives and the claims hereof should not be limited tostructures or methods capable of achieving these objectives.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Other objects, features and advantages will occur to those skilled inthe art from the following description of a preferred embodiment and theaccompanying drawings, in which:

FIG. 1 is a schematic block diagram showing the primary components ofone example of the system for non-invasively determining an indicationand/or an assessment of ICP shown in place above the cranium of a livingsubject;

FIG. 2 is a schematic block diagram showing in further detail theintracranial light source and the extracranial light source shown inFIG. 1;

FIG. 3 is a schematic block diagram showing in further detail oneexample of the spacing of the intracranial light source, theextracranial light source, and the detector shown in FIGS. 1 and 2;

FIG. 4 is a schematic block diagram showing one example of theintracranial light source and the extracranial light source shown in oneor more of FIGS. 1-3 each including at least two light sources;

FIG. 5 is a schematic block diagram showing examples of additionallocations for the placement of the extracranial light source on a livingsubject;

FIG. 6 is a schematic block diagram showing in further detail oneexample of the spacing of the extracranial light source and the detectorshown in FIG. 5;

FIG. 7 is a schematic block diagram showing in further detail oneexample of the spacing of the intracranial light source and the detectorshown in FIG. 5;

FIG. 8 is a schematic block diagram showing one example of theextracranial light source shown FIG. 5 including at least two lightsources;

FIG. 9 is a schematic block diagram showing one example of theintracranial light source shown FIG. 5 including at least two lightsources; and

FIG. 10 is a flowchart showing one example of the primary steps of themethod for non-invasively determining an indication and/or an assessmentof intracranial pressure.

DETAILED DESCRIPTION OF THE INVENTION

Aside from the preferred embodiment or embodiments disclosed below, thisinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Thus, it is to be understood that theinvention is not limited in its application to the details ofconstruction and the arrangements of components set forth in thefollowing description or illustrated in the drawings. If only oneembodiment is described herein, the claims hereof are not to be limitedto that embodiment. Moreover, the claims hereof are not to be readrestrictively unless there is clear and convincing evidence manifestinga certain exclusion, restriction, or disclaimer.

Conventional optical sensing systems, particularly those using nearinfrared (NIR) light, have been used to monitor both blood volumeoscillations and blood oxygen content by using a light source anddetector placed on the skin. In brain related applications, nearinfrared spectroscopy (MRS) may be used to detect changes in oxygenationattributed to regional brain activity or to infer information associatedwith cerebral blood flow and cerebral blood volume and evaluate basicbrain functions. See, e.g., Megumi Mizuno et al., A Functional NIRSStudy of Brain Functional Networks Induced by Social Time Coordination,Brain Sci., 9, 43 (2019), incorporated by reference herein. If nearinfrared light is highly sensitive to the oxygen saturation ofhemoglobin, then its large penetration depth inside tissue implies thatthe arterial, venous, and capillary compartments all contribute to theoptical signal. The average hemoglobin oxygenation measured with NIRS isoften referred to as oxygen tissue saturation (StO₂). See, e.g., Olssonet al., Regional Cerebral Saturation Monitoring with Near-InfraredSpectroscopy During Selective Antegrade Cerebral Perfusion: DiagnosticPerformance and Relationship to Postoperative Stroke. The Journal ofThoracic and Cardiovascular Surgery, Vol. 131, No. 2 (February 2005),incorporated by reference herein. StO₂ values are assumed to be inbetween arterial saturation (SaO₂) and local venous saturation (SvO₂)values. The contribution of the arterial compartment to the non-invasiveoptical signal can be isolated because of its unique temporal dynamicsassociated with the systolic-diastolic blood pressure at the heartbeatfrequency, thus allowing SaO₂ retrieval. SvO₂ can be estimated byisolating the oscillatory components at the respiratory frequency as aresult of the so-called respiratory pump that makes the venous bloodvolume oscillate at the respiratory frequency. See e.g., Franceschini etal., Near-Infrared Spiroximetry: Noninvasive Measurements of VenousSaturation in Piglets and Living Subjects, J. Appl. Physiol., 92 (1)(1985), incorporated by reference herein. SaO₂ is known to reflectinformation about the ventilation and oxygen exchange in lungs whileSvO₂ is a parameter that reflects the local balance between blood flowand oxygen consumption. See e.g., Franceschini et al., cited supra.Therefore, measuring intracranial (cerebral) oxygen saturation andextracranial (extracerebral) oxygen saturation and determining a ratioof intracranial (cerebral) oxygen saturation to extracranial(extracerebral) oxygen saturation may provide a unique avenue intocerebral hemodynamics that have been impacted by ICP thus providingmeans for determining of an indication and/or assessment of ICP, asdiscussed in detail below.

There is shown in FIG. 1 one embodiment of system 10 for non-invasivelyassessing ICP by measuring oxygen saturation. System 10 includes atleast one intracranial or cerebral light source 12 adapted to be placedon skin 14 above cranium 16 of living subject 18. Cranium 16 is shown inphantom in greater detail in FIG. 2. At least one intracranial lightsource 12, FIGS. 1 and 2 emits light 20, shown in greater detail in FIG.3, which penetrates cranium 16 and targets intracranial space 22 asshown. Intracranial space 22 of cranium 16 includes at least brain 23,FIG. 2, of living subject 18. Brain 23 includes, inter alia, thecerebrum, the cerebellum, and the like, as known by those skilled in theart. In this example, living subject 18 is a human subject. In otherexamples, living subject 18 may be any type of living animal that mayexperience ICP.

System 10, FIGS. 1-3, also includes at least one extracranial orextracerebral light source 24, FIGS. 1-3, adapted to be placed on skin14 above a predetermined area of the living subject. In this example,the predetermined area of living subject 18, FIG. 1, is skin 14 abovecranium 16, e.g., on forehead 25. FIGS. 1 and 2. At least oneextracranial light source 24 may also be adapted to be placed on theskirt of any desired predetermined area of living subject 18, e.g, ear92, FIG. 1, torso 94, either of arms 96, 98, either of hands 100, 102,any of lingers 104, 106, either of legs 108, 110, any of toes 116, 118,or back 120, as discussed in further detail below. At least oneextracranial light source 24 emits light 26, FIGS. 2-3, which penetratesand targets extracranial space 28 of living subject 18 as shown.

System 10, FIGS. 1-3, also includes detector subsystem 30 including atleast first detector 32 which detects reflected light 20, FIGS. 2-3,from intracranial space 22 and reflected light 26 from extracranialspace 28. First detector 30 also outputs intracranial output signalsassociated with light 20 detected from intracranial space 22 andextracranial output signals associated with light 26 detected fromextracranial space 28.

In one example, at least one intracranial light source 12 FIGS. 1-3,and/or at least one extracranial light source 24 preferably includes oneor more of a near infrared (NIR) light source, at least one lightemitting diode (LED), and/or an array of photodiodes orphototransistors.

System 10 also includes processing subsystem 40 coupled to at least oneintracranial light source 12, e.g., by line 36, FIG. 3, at least oneextracranial light source 24 by line 38, and detector subsystem 30 withfirst detector 32 by line 34 as shown. Processing subsystem 40, FIGS.1-3, is configured to non-invasively determine intracranial oxygensaturation and extracranial oxygen saturation (See e.g., Yanagisawa etal., Partial Optical Path Length in the Scalp in Subject-Specific HeadModels For Multi-Distance Probe Configuration of Near InfraredSpectroscopy, Proceedings Volume 10711, Biomedical Imaging and SensingConference, (2018), incorporated by reference herein) and non-invasivelydetermine an indication and/or an assessment of ICP using a ratio of theintracranial oxygen saturation to the extracranial oxygen saturation, asdiscussed in further detail below.

StO₂ requires quantitative measurements of oxyhemoglobin anddeoxyhemoglobin concentration. SaO₂ and SvO₂ can be calculated by eitherhaving access to quantitative measurements of oxyhemoglobin anddeoxyhemoglobin concentration or from measuring the amplitude of theoptically measured oxyhemoglobin and deoxyhemoglobin concentrationoscillations by detector subsystem 30 preferably including firstdetector 32 at the cardiac and respiratory frequency respectively.Oscillatory components of oxyhemoglobin and deoxyhemoglobinconcentration at the heart rate and breathing rate are mostlyrepresentative of the arterial and venous compartments. See, e.g.,Franceschini et al., cited supra. Processing subsystem 40 preferablyperforms basic signal processing for oxyhemoglobin and deoxyhemoglobinconcentration calculation. See, e.g., Franceschini et al., cited supra,and Franceschini et al., Noninvasive Optical Method of Measuring Tissueand Arterial Saturation: An Application to Absolute Pulse Oximetry ofthe Brain, Opt. Lett. 24(12) (1999), incorporated by reference herein,and/or to extrapolate the predetermined frequency components of interest(cardiac and breathing rate) in order to use hemoglobin concentrationoscillations for saturation calculation purposes.

FIG. 2 shows one example of the intracranial or cerebral (PenetratingNIR Signal) output signals, indicated at 42, also referred to herein asCerebral (SvO₂) output signals, output by first detector 32 in responseto reflected light 20 also shown in FIG. 3, detected from intracranialspace 22 and extracranial or extracerebral (Superficial NIR signal)output signals, indicated at 44 FIG. 3, also referred to asExtra-cerebral (SvO₂) output signals, output by first detector 32 inresponse to reflected light 26 detected from extracranial space 28.Processing subsystem 40 preferably separates the extracranialcontribution from the intracranial signals for each wavelength thencomputes intracranial or cerebral SvO₂ and extracranial or extracerebralSvO₂, indicated at 46, 48, respectively.

In this example, processing subsystem 40 non-invasively determines anindication and/or an assessment of ICP using a ratio of the intracranialoxygen saturation to the extracranial oxygen saturation using equation(1):SvO _(2_) Rt=SvO ₂ ^(CER) /SvO ₂ ^(EXTRA)  (1)where SvO_(2_)Rt is the oxygen saturation ratio, SvO₂ ^(CER) is thecerebral or intracranial oxygen saturation and SvO₂ ^(EXTRA) is theextracerebral or extracranial oxygen saturation. Processing subsystemmay use venous oxygen saturation, arterial oxygen saturation, or acombination of both. Thus, processing subsystem preferablynon-invasively determines an indication and/or an assessment of ICPusing the ratio of the intracranial oxygen saturation to theextracranial oxygen saturation shown generally in equation (2) below:Ratio=(intracranial oxygen saturation)/(extracranial oxygensaturation)  (2)

In another example processing subsystem 40 may non-invasively determinean indication and/or an assessment of ICP using equation (3) below:ICP=K ₁*(Ratio)+K ₂*(intracranial oxygen saturation)+K ₃*(extracranialoxygen saturation)+K ₄  (3)where K₁, K₁ and K₃ are positive or negative constants and K₄ is anoffset. Thus, depending on the sign of K₂ and K₃ (positive or negative),equation (3) covers difference as well as the addition of theintracranial oxygen saturation and the extracranial oxygen saturation.

In one example, the determination of ICP may be achieved by using amathematical function that relates ICP to the oxygen saturation ratio orby implementing characteristic curves (or look up table) that which holda sequence of ratio values and an ICP value for each. In cases where aspecified ratio value is found to be between two ICP values in thecharacteristic curve, interpolation techniques can be applied betweenthe closest ratio values on the curve, above and below the specifiedratio value, as known to one skilled in the art.

In yet another example, processing subsystem 40 may non-invasivelydetermine an indication and/or an assessment of ICP using a non-linearfunction of the ratio defined in equation (2), the intracranial oxygensaturation and the extracranial oxygen saturation, such as anexponential function or a function derived by curve-fittingrepresentative data.

In one design, at least one intracranial light source 12, FIGS. 1-3,and/or at least one extracranial light source 24 preferably emit lighthaving a wavelength in the range of about 500 nm to about 1,000 nm. Inother examples, at least one intracranial light source 12 and/or atleast the extracranial light source 24 may emit light having wavelengthsgreater or less than the range of about 500 nm to 1,000 nm as known bythose skilled in the art.

In one example, at least one intracranial light source 12 preferablyincludes at least two light sources, e.g., intracranial light source 52,FIG. 4, where like parts have been given like numbers, and intracraniallight source 54. One of intracranial light sources 52 or 54 preferablyemits light at one or more first predetermined wavelengths, e.g., atabout 690 nm, and the other of intracranial light sources 52 and 54preferably emits at one or more second predetermined wavelengths, e.g.,at about 830 nm. Other one or more first and second predeterminedwavelengths may also be utilized as known by those skilled in the art.In this example, intracranial light source 52 preferably emits light 56at the first predetermined wavelength and intracranial light source 54preferably emits light 58 at the second predetermined wavelength whichare both detected by first detector 32 as shown. Preferably, one of thefirst predetermined wavelengths or the second predetermined wavelengthstargets oxyhemoglobin chromophores and the other of the first or secondpredetermined wavelengths targets the deoxyhemoglobin chromophores, asknown by those skilled in the art. See, e.g., Zhao et al., OptimalHemoglobin Extinction Coefficient Data Set For Near-InfraredSpectroscopy, Biomed Optical Express, 8(11) (2017), incorporated byreference herein.

Similarly, at least one extracranial light source 24, FIGS. 1-3, mayalso preferably include at least two light sources, e.g., extracraniallight source 60, FIG. 4, and extracranial light source 62. One ofextracranial light sources 60 or 62 preferably emits light at one ormore first predetermined wavelengths, e.g., at about 690 nm, and theother of extracranial light sources 60 and 62 preferably emits at one ormore second predetermined wavelengths, e.g., at about 830 nm. Additionalfirst and second predetermined wavelengths other than the wavelengthsdiscussed above may also be utilized as known by those skilled in theart. In this example, light source 60 preferably emits light 66 at thefirst predetermined wavelength and light source 62 preferably emitslight 68 at the second predetermined wavelength which are both detectedby detector 32 as shown. Preferably, one of the first or secondpredetermined wavelengths targets oxyhemoglobin chromophores and theother of the first or second predetermined wavelengths targets thedeoxyhemoglobin chromophores, as known by those skilled in the art.

In one example, at least one intracranial light source 12 shown in oneor more of FIGS. 1-4, may be adapted to be placed on skin 14 abovecranium 16 of living subject 18 with the at least one extracranial lightsource 24 located between at least one intracranial light source 12 andfirst detector 32, e.g., as shown in FIGS. 3 and 4.

In one example, first detector 32 shown in one or more of FIGS. 1-4 ispreferably spaced from at least one intracranial light source 12 byintracranial separation distance d-80, FIGS. 3 and 4, that causes firstdetector 32 to detect light 20, FIGS. 2 and 3, or light 56, 58, FIG. 4,reflected from intracranial space 22 and output the intracranial outputsignals to processing subsystem 40. Similarly, first detector 32 may bespaced from extracranial light source 24 by extracranial separationdistance d-82, FIGS. 3 and 4, that causes first detector 32 to detectlight 26, FIGS. 2 and 3, or light 66, 68, FIG. 4, reflected fromextracranial space 28 and output the extracranial output signals toprocessing subsystem 40.

In one design, processing subsystem 40, FIGS. 1-4, preferably enables atleast one intracranial light source 12 and at least one extracraniallight source 24 and alternately enables first detector 32 to detectlight 20, FIGS. 2 and 3, or light 56, 58, FIG. 4, which reflects fromintracranial space 22 and light 26, FIGS. 2 and 3, or light 66, 68, FIG.4, which reflects from extracranial space 28 and generate theintracranial output signals and extracranial output signals,respectively. Processing subsystem 40 is also preferably responsive tothe intracranial output signals and the extracranial output signals andpreferably reduces contributions from extracranial space 28 which mayexist in the intracranial output signals and generate correctedintracranial output signals to increase the accuracy of the indicationof ICP.

In one example, the intracranial oxygen saturation, e.g., cerebraloxygen saturation and/or the extracranial oxygen saturation includes oneor more of oxygen tissue saturation (StO₂), arterial oxygen saturation(SaO₂), or venous oxygen saturation (SvO₂).

As discussed above with reference to one or more of FIGS. 1-4, at leastone extracranial light source 24 is shown adapted to be placed on skin14 above the predetermined area of the living subject 18 depicted ascranium 16. In other examples, system 10′, FIG. 5, where like parts havebeen given like numbers, preferably includes extracranial light source24 adapted to be placed on the skin above of any desired predeterminedarea of living subject 18, e.g., ear 92, torso 94, either of arms 96,98, either of hands 100, 102, any of fingers 104, 106, either of legs108, 110, any of toes 116, 118, or back 120 of living subject 18, asexemplarily shown in FIG. 5.

When at least one extracranial light source 24 is placed on apredetermined area other than cranium 16, e.g., any of predeterminedareas 92-120 discussed above, detector subsystem 30 preferably includessecond detector 122 adapted to be placed proximate the location ofextracranial light source 24 placed at the predetermined location otherthan cranium 16, e.g., as exemplarily shown in FIG. 5. In this design,second detector 122 may also be referred to as extracranial detector122. In this example, first detector 32 located on skin 14 above cranium16 is responsive only to light 20, FIG. 7, reflected from intracranialspace 22 emitted by at least one intracranial light source 12 asdiscussed below. First detector 32 may also be referred to herein asintracranial detector 32.

In this example, at least one extracranial light source 24, FIG. 5, isshown placed on the skin above arm 96 and coupled to processingsubsystem 40 by line 134. Second or extracranial detector 122 is placedproximate at least one extracranial light source 24 as shown and iscouple to processing subsystem 40 by line 126. In other examples, atleast one extracranial light source 24 and second or extracranialdetector 122 may be placed proximate each other on any of predeterminedarea 92-120 as discussed above and as exemplarily shown, and similarlycoupled to processing subsystem 40.

Similar as discussed above with reference to one or more of FIGS. 1-4,at least one extracranial light source 24, FIG. 5, located at any ofpredetermined areas 92-120, emits light 26, FIG. 6, which penetrates andtargets extracranial space 28 of the predetermined area where at leastone extracranial light source is located. Second or extracranialdetector 122 located proximate at least one extracranial light source 24detects reflected light 26 from extracranial space 22 and outputsextracranial output signals associated with light 26 detected fromextracranial space 28 to processing subsystem 40.

Similar as discussed above, with reference to one or more of FIGS. 1-4,system 10′ includes at least one intracranial light source 12, FIG. 5,adapted to be placed on skin 14 above cranium 16. At least oneintracranial light source 12, FIGS. 5 and 7, emits light 20, FIG. 7,which penetrates cranium 16 (shown in greater detail in FIG. 2) andtargets intracranial space 22. First or intracranial detector 32, FIGS.5 and 7, detect reflected light 20 from intracranial space 22 outputsintracranial output signals associated with light 20 detected fromintracranial space 22 to processing subsystem 40.

Processing subsystem 40, FIGS. 5-7 is preferably coupled to at least oneintracranial light source 12, at least one extracranial light source 24,first or intracranial detector 32 and second or extracranial detector122 as shown and is responsive to intracranial output signals andextracranial output signals. Similar as discussed above with referenceto one or more of FIGS. 1-4, processing subsystem 40, FIGS. 5-7, ispreferably configured to determine intracranial oxygen saturation andextracranial oxygen saturation non-invasively determine an indicationand/or an assessment of ICP using a ratio of the intracranial oxygensaturation to the extracranial oxygen saturation.

Extracranial light source 24, FIGS. 5 and 6, placed on any ofpredetermined area 92-120, FIG. 5, of living subject 18 discussed abovemay include at least two light sources, extracranial light source 60,FIG. 8, and extracranial light source 62 which operate similar asdiscussed above with reference to at least FIG. 4 to preferably emitlight 64, 66 at one or more first and second predetermined wavelengths.

At least one intracranial light source 12, FIGS. 5 and 7, placed on theskin above cranium 16 may also include at least two light sources, e.g.,first light source 52, FIG. 9, and second light source 54 which operatesimilar as discussed above with reference to at least FIG. 4 topreferably emit light 56, 58 at one or more first and secondpredetermined wavelengths.

Similar as discussed above with reference to one or more of FIGS. 1-4,first or intracranial detector 32, FIGS. 5, 7 and 9, is preferablyspaced from at least one intracranial light source 12 by intracranialseparation distance d-80, FIGS. 7 and 9, that causes first orintracranial detector 32 to detect light 20, FIG. 7, or light 56, 58,FIG. 9, reflected from intracranial space 22 and output the intracranialoutput signals to processing subsystem 40.

Second or extracranial detector 122, FIGS. 5, 6 and 8, is alsopreferably spaced from at least one extracranial light source 24 bypredetermined extracranial separation distance d-82, FIGS. 6 and 8, thatcauses second detector 122 to detect light 26, FIG. 6 or light 64, 66,FIG. 8, which is reflected from extracranial space 28 located at any ofpredetermined areas 92-120, FIG. 5, in this example arm 96, and outputextracranial output signals, e.g., by line 126, FIGS. 6 and 8 toprocessing subsystem 40. Although in this example second or extracranialdetector 122 is placed proximate extracranial light source 24 located onarm 96 of living subject 18, in other examples, second detector 122 maybe placed on any of the predetermined areas 92-120 discussed above andshown in FIG. 5 and predetermined extracranial separation distance,d-82, is preferably determined in a similar manner.

Similar as discussed above with reference to one or more of FIGS. 1-4,processing subsystem 40, FIGS. 5-9, preferably alternately enables atleast one intracranial light source 12 and at least one extracraniallight source 122 and alternately enables first or intracranial detector32 to detect light reflected from intracranial space 22 and alternatelyenable second or extracranial detector 122 to detect light 26 reflectedfrom extracranial space 28 and generate the intracranial output signalsand the extracranial output signals. Processing subsystem 40 alsopreferably reduces contributions from extracranial space 28, FIGS. 6-9,which may exist in the intracranial output signals and generatecorrected intracranial output signals to increase the accuracy of theindication of ICP.

Processing subsystem 40 shown in one ore more of FIGS. 1-8 may includeone or more processors, e.g., processor 42. Processing subsystem 40 mayalso be configured as an application-specific integrated circuit (ASIC),firmware, hardware, and/or software (including firmware, residentsoftware, micro-code, and the like) or a combination of both hardwareand software that may all generally be referred to herein as “processingsubsystem 40”. Computer program code for the programs for carrying outthe instructions or operation of processing subsystem 40 may be writtenin any combination of one or more programming languages, including anobject-oriented programming language, e.g., C++, Smalltalk, Java, andthe like, or conventional procedural programming languages, such as the“C” programming language or similar programming languages.

The determined indication and/or an assessment of ICP discussed abovewith reference to one or more of FIGS. 1-9 is not an actual measured ICPwhich is typically measured in mmHg. Instead, the indication and/orassessment of ICP is calculated or determined using the ratio of themeasured intracranial or cerebral oxygen saturation to the measuredextracranial or extracerebral oxygen saturation discussed above ispreferably displayed on a device, e.g., display device 152, e.g., amonitor of a personal computer, a smart device, such as smart phone ortablet, or similar type device. Display device 152 preferably displaysone or more of the indication and/or assessment of ICP, the intracranialor cerebral oxygen saturation and/or the extracranial car extracerebraloxygen saturation and/or a ratio and/or difference of the intracranialor cerebral oxygen saturation and the extracranial or extracerebraloxygen saturation as discussed above.

System 10, 10′ shown in one or more of FIGS. 1-9, preferably includesstorage device 154 configured to store data associated with theintracranial signals, the extracranial signals, the extracranial oxygensaturation, the intracranial oxygen saturation, and the indication ofICP.

Systems 10, 10′, FIGS. 1-9 also preferably includes a power supplycoupled to at least one intracranial light source 12, at least oneextracranial light source 24, first or intracranial detector 32, secondor extracranial detector 122, processing subsystem 40 and/or display 152e.g., exemplarily shown by power supply 152, FIGS. 1-9.

One example of the method for non-invasively determining and/orassessing ICP preferably includes emitting light which penetrates acranium of a living subject, step 200, FIG. 10, and emitting light whichpenetrates and targets the extracranial space of a living subject, step202. The method also includes detecting light reflected from theintracranial space and outputting intracranial output signals, step 204,and detecting light reflected from the extracranial space and outputtingextracranial output signals, step 206. The method also includesresponding to the intracranial output signals and the extracranialoutput signals and determining intracranial oxygen saturation andextracranial oxygen saturation and non-invasively determining anindication and/or an assessment of ICP using a ratio of the intracranialoxygen saturation to the extracranial oxygen saturation, step 208.

Preferably, the step of emitting light which penetrates the cranium ofthe living subject and targets the intracranial space and emitting lightwhich penetrates and targets the extracranial space of the livingsubject includes emitting light having a wavelength in the range ofabout 500 nm to about 1,000 nm. Emitting light which penetrates thecranium of the living subject and targets the intracranial spacepreferably includes emitting light at one or more first predeterminedwavelengths and emitting light at one or more second predeterminedwavelengths, as discussed above with reference to one or more of FIGS.1-9. Preferably, emitting light which penetrates and targets theextracranial space of the living subject includes emitting light at oneor more first predetermined wavelengths and emitting light at one ormore second predetermined wavelengths, as discussed above with referenceto one or more of FIGS. 1-9. Preferably, one of the first predeterminedwavelengths or the second predetermined wavelengths target oxyhemoglobinchromophores and the other of the first predetermined wavelengths, orsecond predetermined wavelengths target deoxyhemoglobin chromophores, asdiscussed above with reference to one or more of FIGS. 1-9.

The result is the arrangement and use of at least one intracranial lightsource that emits light that penetrates the cranium and targetsintracranial space of a living subject, at least one extracranial lightsource that emits light which penetrates and targets extracranial spaceof the living subject, a detector subsystem that detects reflected lightfrom the intracranial space and the extracranial space, and a processingsubsystem that determines intracranial oxygen saturation andextracranial oxygen saturation non-invasively determines an indicationand/or an assessment of ICP using a ratio of the intracranial oxygensaturation to the extracranial oxygen saturation provides an accurate,effective and timely indication and/or assessment of ICP. Thus, system10 and the method thereof may efficiently, effectively, and timelyprovide medical care those who may have experienced trauma to the brain.Additionally, system 10 may be more compact, inexpensive, robust, andpower efficient system than conventional invasive systems discussed inat least the Background section above.

Although specific features of the invention are shown in some drawingsand not in others, this is for convenience only as each feature may becombined with any or all of the other features in accordance with theinvention. The words “including”, “comprising”, “having”, and “with” asused herein are to be interpreted broadly and comprehensively and arenot limited to any physical interconnection. Moreover, any embodimentsdisclosed in the subject application are not to be taken as the onlypossible embodiments.

In addition, any amendment presented during the prosecution of thepatent application for this patent is not a disclaimer of any claimelement presented in the application as filed: those skilled in the artcannot reasonably be expected to draft a claim that would literallyencompass all possible equivalents, many equivalents will beunforeseeable at the time of the amendment and are beyond a fairinterpretation of what is to be surrendered (if anything), the rationaleunderlying the amendment may bear no more than a tangential relation tomany equivalents, and/or there are many other reasons the applicantcannot be expected to describe certain insubstantial substitutes for anyclaim element amended.

Other embodiments will occur to those skilled in the art and are withinthe following claims.

What is claimed is:
 1. A system for non-Invasively determining anindication or an assessment of Intracranial pressure (ICP), the systemcomprising: at least one intracranial light source adapted to be placedon skin above a cranium of a living subject configured to emit lightwhich penetrates the cranium and targets intracranial space of theliving subject; at least one extracranial light source adapted to beplaced on skin above a predetermined area of the living subjectconfigured to emit light which penetrates and targets extracranial spaceof the living subject; a detector subsystem including at least a firstdetector configured to detect reflected light from the intracranialspace and light refected from the extracranial space and configured tooutput intracranial output signals associated with light detected fromthe intracranial space and output extracranial output signals associatedwith the light detected from the extracranial space; and a processingsubsystem coupled to the at least one intracranial light source, the atleast one extracranial light source, and the detector subsystem, theprocessing subsystem configured to determine intracranial oxygensaturation and extracranial oxygen saturation and non-invasivelydetermine the indication or the assessment of ICP using a ratio of theintracranial oxygen saturation to the extracranial oxygen saturation. 2.The system of claim 1 in which the at least one intracranial lightsource includes at least two light sources, one of the two lightssources configured to emit light at one or more first predeterminedwavelengths and the other of the at least two light sources configuredto emit light at one or more second predetermined wavelengths.
 3. Thesystem of claim 1 in which the at least one extracranial light sourceincludes at least two light sources, one of the two light sourcesconfigured to emit light at one or more first predetermined wavelengthsand the other of the at least two light sources configured to emit lightat one or more second predetermined wavelengths.
 4. The system of claim2 in which one of the first predetermined wavelengths or the secondpredetermined wavelengths is configured to target oxyhernoglobinchromophores and the other of the first predetermined wavelengths orsecond predetermined wavelengths is configured to target deoxyhemoglobinchromophores.
 5. The system of claim 3 in which one of the firstpredetermined wavelengths or the second predetermined wavelengths isconfigured to target oxyhemoglobin chromophores and the other of thefirst predetermined wavelengths or second predetermined wavelengths isconfigured to target deoxyhemoglobin chromophores.
 6. The system ofclaim 1 in which the at least one intracranial light source, the atleast one extracranial light source, and the detector subsystem areadapted to be placed on the skin above the cranium of the living subjectwith the at least one extracranial light source located between the atleast one intracranial light source and the first detector.
 7. Thesystem of claim 1 in which the at least one first detector is spacedfrom the at least one intracranial light source by an intracranialseparation distance that causes first detector to detect the lightreflected from the intracranial space and output the intracranial outputsignals.
 8. The system of claim 1 in which the at least one firstdetector is spaced from the at least one extracranial light source by anextracranial separation distance that causes the at least one firstdetector to detect light reflected from the extracranial space andoutput the extracranial output signals.
 9. The system of claim 1 inwhich the processing subsystem is configured to alternately enable theat least one intracranial light source and the at least one extracraniallight source and alternately enable the first detector to detect thelight which reflects from the intracranial space and the light whichreflects from the extracranial space to generate the intracranial outputsignals and the extracranial output signals, the processing subsystemresponsive to the intracranial output signals and the extracranialoutput signals and further configured to reduce contributions from theextracranial space which may exist in the intracranial output signalsand generate corrected intracranial output signals to increase accuracyof the indication or the assessment of ICP.
 10. The system of claim 1 inwhich the detector subsystem includes a second detector adapted to beplaced on one of the predetermined areas of the living subject.
 11. Thesystem of claim 10 in which the second detector is placed proximate theat least one extracranial light source and spaced from the at least oneextracranial light source by a predetermined extracranial separationdistance that causes the second detector to detect light which isreflected from the extracranial space and output the extracranial outputsignals.
 12. The system of claim 11 in which the processing subsystem iscoupled to the at least one intracranial light source, the at least oneextracranial light source, the first detector, and the second detector,the processing subsystem configured to alternately enable the at leastone intracranial light source and the at least one extracranial lightsource and alternately enable the first detector to detect the lightreflected from the intracranial space and alternately enable the seconddetector to detect the light reflected from the extracranial space andgenerate the intracranial output signals and the extracranial outputsignals and further configured to reduce contributions from theextracranial space that may exist in the intracranial output signals andgenerate corrected intracranial output signals to increase the accuracyof the indication or the assessment of ICP.
 13. The system of claim 1 inwhich the intracranial oxygen saturation or the extracranial oxygensaturation includes one or more of: oxygen tissue saturation (StO₂),arterial oxygen saturation (SaO₂), or venous oxygen saturation (SvO₂).14. The system of claim 1 further including a display device coupled tothe processing subsystem configured to display one or more of: theindication or the assessment of ICP, or the ratio of the intracranialoxygen saturation to the extracranial oxygen saturation, or theintracranial oxygen saturation, or the extracranial oxygen saturation,or a difference of the intracranial oxygen saturation and theextracranial oxygen saturation or an addition of the intracranial oxygensaturation and the extracranial oxygen saturation.
 15. A system fornon-invasively determining an indication or an assessment ofintracranial pressure, the system comprising: at least one intracraniallight source adapted to be placed on skin above a cranium of a livingsubject configured to emit light which penetrates a cranium of a livingsubject and targets intracranial space of the living subject; at leastone intracranial detector, the at least one intracranial detector placedproximate the at least one intracranial light source and spaced from theintracranial light source by a predetermined intracranial separationdistance that causes the intracranial detector to detect the light whichreflects from the intracranial space and output intracranial outputsignals; at least one extracranial light source adapted to be placed onthe skin above a predetermined area of the living subject configured toemit light which penetrates and targets extracranial space of the livingsubject; at least one extracranial detector, the at least oneextracranial detector placed proximate the at least one extracraniallight source and spaced from the at least one extracranial light sourceby a predetermined extracranial separation distance that causes the atleast one extracranial detector to detect the light which reflects fromthe extracranial space and output extracranial output signals; and aprocessing subsystem coupled to the at least one intracranial lightsource, the at least one intracranial light detector, the at least oneextracranial light source, and the at least one extracranial detector,the processing subsystem configured to determine intracranial oxygensaturation and extracranial oxygen saturation and non-invassvelydetermine the indication or the assessment of ICP using a ratio of theintracranial oxygen saturation to the extracranial oxygen saturation.16. The system of claim 15 in which the processing subsystem isconfigured to alternately enable the at least one intracranial lightsource and the at least one extracranial light source and alternatelyenable the at least one intracranial detector to detect the lightreflected from the intracranial space and alternately enable the atleast one extracranial detector to detect light which reflects lightwhich reflects from the extracranial space to generate the intracranialoutput signals and the extracranial output signals, the processingsubsystem responsive to the intracranial output signals and theextracranial output signals and further configured to reducecontributions from the extracranial space which may exist in theintracranial output signals and generate corrected intracranial outputsignals to increase accuracy of the indication and/or assessment of ICP.17. The system of claim 15 in which the at least one intracranial lightsource includes at least two light sources, one of the two lightssources configured to emit light at one or more first predeterminedwavelengths and the other of the at least two light sources configuredto emit light at one or more second predetermined wavelengths.
 18. Thesystem of claim 15 in which the at least one extracranial light sourceincludes at least two light sources, one of the two light sourcesconfigured to emit light at one or more first predetermined wavelengthsand the other of the at least two light sources configured to emit lightat one or more second predetermined wavelengths.
 19. The system of claim17 in which one of the first predetermined wavelengths or the secondpredetermined wavelengths is configured to target oxyhemoglobinchromophores and the other of the first predetermined wavelengths orsecond predetermined wavelengths is configured to target deoxyhemoglobinchromophores.
 20. The system of claim 18 in which one of the firstpredetermined wavelengths or the second predetermined wavelengths isconfigured to target oxyhemoglobin chromophores and the other of thefirst predetermined wavelengths or second predetermined wavelengths isconfigured to target deoxyhemoglobin chromophores.
 21. The system ofclaim 15 in which the at least one intracranial detector is spaced fromthe at least one intracranial light source by an intracranial separationdistance that causes at least one intracranial detector to detect thelight reflected from the intracranial space and output the intracranialoutput signals.
 22. The system of claim 15 in which the at least oneextracranial detector is spaced from the at least one extracranial lightsource by an extracranial separation distance that causes the at leastone extracranial detector to detect light reflected from theextracranial space and output the extracranial output signals.
 23. Thesystem of claim 15 in which the intracranial oxygen saturation and/orthe extracranial oxygen saturation includes one or more of oxygen tissuesaturation (StO₂), arterial oxygen saturation (SaO₂), or venous oxygensaturation (SvO₂).
 24. The system of claim 15 further including adisplay device coupled to the processing subsystem configured to displayone or more of: the indication and/or assessment of ICP, and/or theratio of the intracranial oxygen saturation to the extracranial oxygensaturation, and/or the intracranial oxygen saturation, and/or theextracranial oxygen saturation, and/or a difference of the intracranialoxygen saturation and the extracranial oxygen saturation and/or anaddition of the intracranial oxygen saturation and the extracranialoxygen saturation.
 25. A method for non-invasively determining anindication or an assessment of intracranial pressure by measuring oxygensaturation, the method comprising: emitting light which penetrates acranium of a living subject and targets intracranial space of the livingsubject; emitting light which penetrates and targets extracranial spaceof a predetermined area of the living subject; detecting light reflectedfrom the intracranial space outputting intracranial output signals;detecting light reflected from the extracranial space and outputtingextracranial output signals; responding to the intracranial outputsignals and the extracranial output signals determining intracranialoxygen saturation and extracranial oxygen saturation and non-invasivelyand determining the indication or the assessment of ICP using a ratio ofthe intracranial oxygen saturation to the extracranial oxygensaturation.
 26. The method of claim 25 in which emitting light whichpenetrates the cranium of the living subject and targets theintracranial space includes emitting, light at one or more firstpredetermined wavelengths and emitting light at one or more secondpredetermined wavelengths, one or more of the first predeterminedwavelengths configured to target ox hemoglobin chromophores and theother of the one or more first predetermined wavelengths or secondpredetermined wavelengths configured to target deoxyhemoglobinchromophores.
 27. The method of claim 25 in which emitting light whichpenetrates and targets the extracranial space of the living subjectincludes emitting light at one or more first predetermined wavelengthsand emitting light at one or more second predetermined wavelengths, oneof the one or more first predetermined wavelengths configured to targetoxyhemoglobin chromophores and the other of the one or more firstpredetermined wavelengths or one or more second predeterminedwavelengths configured to target deoxyhemoglobin chromophores.
 28. Themethod of claim 25 further including alternately emitting light whichpenetrates the cranium of the living subject and targets theintracranial space of the living subject and emitting light whichpenetrates and targets the extracranial space of the predetermined areaof the living subject and alternately detecting light reflected from theintracranial space and outputting the extracranial signals andalternately detecting light reflected from the extracranial space andoutputting the extracranial signals and reducing contributions from theextracranial space that may exist in the intracranial output signals andgenerating corrected intracranial output signals to increase an accuracyof the indication or the assessment of ICP.